Process for production of an ether-rich additive

ABSTRACT

A process for the production of an ether-rich additive for gasoline, and more particularly, the production of MTBE, TAME and mixtures thereof from light hydrocarbon streams comprising passing the light hydrocarbon stream, preferably from an FCC feedstock, through a superactivated porous particulate medium so as to remove nitrogen compounds, mercaptan and water prior to contacting the feedstock with a catalyst under etherification process conditions. The present invention further includes a process for regenerating the spent superactivated mediums used for purifying the feedstock employed in the process for the production of ether-rich additives for gasoline.

This application is a continuation-in-part of co-pending and commonlyassigned U.S. patent application No. 07/847,194, filed Mar. 6, 1992, nowU.S. Pat. No. 5,210,326.

BACKGROUND OF THE INVENTION

The present invention relates to a process for the production ofether-rich additives for gasoline, and, more particularly, the.production of MTBE, TAME or mixtures thereof from light hydrocarbonstreams.

MTBE, TAME or mixtures thereof are used extensively as fuel extendersand octane value improving agents in the production of unleadedgasoline. Generally, but for the inclusion of such fuel extenders andoctane value improving agents, acceptable octane values can only beobtained by varying the compounding additives in the gasoline, that is,increasing the lead content of the gasoline. The desirability of leadfree gasolines is clearly recognized. Lead additives in gasolines resultin the emission of pollutants in exhaust gases from internal combustionengines thereby contributing to overall environmental pollution. Theemployment of substitutes for lead in gasoline compounds which improvethe octane value of the gasoline will lead to a cleaner burning gasolinethereby improving air quality and the overall environmental condition.

There are many processes developed in the prior art for producing MTBE(methyl t-butyl ether) and TAME (methyl t-amyl ether). Typicaletherification processes are disclosed in U.S. Pat. Nos. 5,001,292;4,925,455; 4,827,045; and U.S. Pat. No. 4,830,635 to Harandi et al.Other known processes include that disclosed in U.S. Pat. No. 4,025,989to Hagan et al. For the most part, these known processes for preparingethers as additives for gasoline comprise reacting a primary alcohol,such as methanol, with an olefin having a double bond on a tertiarycarbon atom, such as, isobutylene and isopropentene. It is known in theprior art to react the alcohol and the olefin in the presence of acatalyst. Suitable known catalysts include Lewis acids (sulfuric acid)and organic acids (alkyl and aryl sulfonic acids). A particularlysuitable catalyst for these reactions are ion exchange resins in theiracid form of the type marketed under the trademark "AMBERLIST 15" whichis a trademark of Rohm and Haas, or Bayer product K2631. While manyhydrocarbon feedstocks may be used for the manufacture of MTBE and TAMEit is particularly useful in the petroleum refining operation to processMTBE and TAME from light hydrocarbon streams resulting from fluidcatalytic cracking (FCC) refinery operations. When processing FCChydrocarbon streams under etherification conditions so as to form MTBEand TAME it has been found that the catalysts used in the process arerapidly poisoned, that is, the catalysts are deactivated. As thecatalyst materials used in known processes are relatively expensive, theforegoing problem of catalyst deactivation leads not only to processinefficiency but also to substantial increases in processing costs. Noneof the prior art processes, and particularly none of the U.S. Patentsdiscussed above, deal satisfactorily with the aforesaid problem.

Naturally, it would be highly desirable to provide a process for theconversion of hydrocarbon streams from FCC refinery processes, to MTBEand TAME which overcome the problems of catalyst poisoning as discussedabove.

Accordingly, it is the principal object of the present invention toprovide a process for the conversion of liquid light hydrocarbon streamsto ether-rich additives such as MTBE and TAME in an efficient andeconomic manner.

It is a particular object of the present invention to provide a processas aforesaid wherein the poisoning of the catalysts used in theetherification process is inhibited.

It is a further object of the present invention to provide a process asaforesaid wherein the liquid light hydrocarbon feedstock fed to theetherification zone is pretreated with a superactivated particulatemedium prior to etherification processing in the presence of thecatalyst.

It is a still further object of the present invention to provide aprocess as aforesaid wherein the alumina medium used in the process ofthe present invention is readily regenerated for further use in theprocess.

Further objects and advantages of the present invention will appearhereinbelow.

SUMMARY OF THE INVENTION

In accordance with the present invention the foregoing objects andadvantages are readily obtained.

The present invention relates to a process for the production ofether-rich additives from light hydrocarbon feedstocks and, moreparticularly, form light hydrocarbon feedstocks having significantconcentrations of nitrogen compounds, mercaptan and water. Suchfeedstocks include light naphtha cut hydrocarbons from FCC processes.The liquid hydrocarbon feedstocks are passed through a medium forremoving the nitrogen compounds, particularly nitrile compounds,mercaptan (thiol) and water from the feedstock so as to form a purifiedfeedstock prior to subjecting the feedstock to etherification processconditions in the presence of the catalyst. In accordance with thepresent invention, the liquid hydrocarbon feedstock is passed through asuperactivated particulate medium where nitrogen compounds, particularlynitrile compounds, mercaptan and water are removed so as to result in apurified feedstock to the etherification zone which is substantiallyfree of nitrogen compounds, mercaptan and water. Suitable particulatemedia include particles of alumina, silica, zeolite, and mixturesthereof. Such particles are superactivated and, after they are spent,such particles are regenerated, in accordance with the present inventionas will be discussed hereinbelow. It has been found in accordance withthe present invention that by pretreating the light hydrocarbonfeedstock as aforesaid, the rate of poisoning of the catalyst employedin the etherification process is greatly reduced thereby increasingprocess efficiency while at the same time decreasing processing costs.

The process of the present invention, in its preferred form, providesfor a plurality of superactivated particulate mediums wherein thefeedstock being treated is passed through one of the plurality ofsuperactivated particulate mediums for purifying same. The purifiedfiltered feedstock is monitored downstream of the particulate medium forsensing when the first medium is spent. When the first medium is spentthe feedstock is passed through another of the plurality of particulatemediums so as to allow the process to proceed in a continuous manner.The spent particulate medium is then subjected to a regeneration processin accordance with the present invention.

The spent superactivated particulate medium is regenerated by drainingthe liquid hydrocarbon feedstock from the medium which is in the form ofa bed of porous particles forming interstitial spaces therebetween. Thedrained bed of particles is thereafter dried with inert gas. Inaccordance with the present invention, the drained and dried particulatemedium is thereafter washed under critical conditions with asuperactivating material in a series of steps to remove carbonaceousmaterials including polymer precursors, to prohibit the formation ofpolymers and to increase the surface area of the particles. The washedparticulate media free of polymers is thereafter dried with inert gas,preferably in a stepwise fashion.

The process of the present invention wherein the feedstock to theetherification reactor is pretreated so as to remove nitrogen compounds,particularly nitrile compounds, mercaptan and water allows for theefficient and economical production of ether-rich additives such as MTBEand TAME by improving the life of the catalyst used in theetherification process. In addition, by providing a process forregenerating the medium used in the pretreatment of the feedstock theoverall process of the present invention is efficient and economical tocarry out.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of the preferred embodiments of the inventionfollows, with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic flow diagram illustrating the process of thepresent invention;

FIG. 2 is a graph demonstrating the adverse effect of nitriles on theacid catalyst activity used in the etherification of light hydrocarbonfeedstocks to TAME and demonstrating the advantages of the process ofthe present invention;

FIG. 3 illustrates the positive effect of the regeneration process ofthe present invention on the nitrile absorption capabilities of analumina medium treated in accordance with the process of the presentinvention;

FIG. 4 illustrates the relation between surface area and temperatures ofregeneration of superactivated alumina, according to the invention, witha water vapor-air mixture to remove any gum or polymer from theabsorbent medium;

FIG. 5 shows the diffraction spectrum of original commercial alumina;and

FIG. 6 shows the diffraction spectrum of superactivated alumina afterregeneration according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, the process of the present invention will bedescribed in detail.

A facility 10 for carrying out the conversion of light hydrocarbonfeedstocks to an ether-rich additive, particularly TAME and MTBE, isillustrated. For purposes of description the process of the presentinvention will be described with reference to light hydrocarbonfeedstocks obtained form FCC process operations, particularly, lightnaphtha cut FCC feeds which are cut in the C₃ -C₇ range and preferablyC₄ and C₅ range.

With reference to FIG. 1, the feedstock from the FCC refinery facility12 is fed to the etherification zone 14 for converting the lighthydrocarbon feedstock to an ether-rich additive, particularly, MTBE andTAME. In accordance with the process of the present invention, thefeedstock from the FCC process 12 is pretreated prior to feeding same tothe etherification zone 14 in purification zone 16 for removing nitrogencompounds, particularly nitriles, mercaptan and water from the lighthydrocarbon feedstock produced by the FCC process in zone 12.

In accordance with the present invention, the typical feedstock producedin the FCC refinery facility 12 which is drawn off via line 18 is alight hydrocarbon naphtha feedstock. In accordance with the preferredembodiment of the present invention the light naphtha cut is C₃ -C₇ cutand preferably substantially a C₄, C₅ cut. The feedstock described abovefor the etherification zone 14 which is produced in the FCC refineryfacility 12 and drawn off via line 18 is characterized by the followingcomposition: isobutene in the range of 10-15 wt. %; isoamylenes in therange of 7-14 wt. %; diolefins in the range of 0.5-1.0 wt. %; amercaptan concentration in the range of 4-6 ppm; a nitrogenconcentration in the range of 17-20 ppm wherein nitriles are present inthe range of 15-17 ppm; and water content in the range of about 30-50ppm.

In accordance with the present invention the feed from the FCC refineryfacility 12 is fed to purification zone 16 prior to delivery to theetherification zone 14 for removing nitriles and other nitrogencompounds, mercaptan and water from the feedstock so as to produce apurified feedstock substantially free of nitrogen compounds,particularly nitriles, mercaptan and water for delivery from thepurification zone 16 via line 20 to the etherification zone 14. Inaccordance with the preferred embodiment of the present invention, thepurified feedstock from the purification zone 16 which is fed via line20 to the etherification zone 14 has a total nitrogen content of lessthan 2 ppm wherein the nitrile content is less than 1 ppm, a totalmercaptan content of less than 1 ppm and a water content of less than 1ppm. It has been found, in accordance with the process of the presentinvention, that by reducing the nitrogen compounds, mercaptan and water(particularly nitriles) the life of the catalyst used in theetherification process in zone 14 is greatly improved. It has been foundthat the nitriles in the feedstock decompose in the etherification zonein the presence of water to form amines which deactivate the catalystemployed in the etherification process, that is, poison the catalyst.

The feedstock from the FCC facility 12 is treated in the purificationzone 16 by passing the feedstock via line 18 through a particulatemedium held in an absorption zone or trap 30. In accordance with thepresent invention a plurality of traps or zones 30 are employed in theprocess of the present invention in a manner to be describedhereinbelow. The particulate medium employed in the process of thepresent invention comprises a bed of porous particles 2 which forminterstitial spaces therebetween when packed into the absorption zone30. Suitable porous particles include particles of alumina, silica,zeolite, and mixtures thereof. A particularly suitable alumina mediumfor use in the process is sold under the trademark SELEXSORB CD and iscommercially available from ALCOA. Typically, the feedstock is passedthrough the medium at a liquid space velocity (LHSV) in the range ofabout 1.0 to about 5.5 v/v/hr. The process conditions are typicallypressure in the range of 100-300 psi and temperature in the range of50°-200° F.

The purified feedstock leaving the trap or zone 30 is continuallymonitored by means of a sensor 34 (to be described in detailhereinbelow) in order to insure that the feedstock delivered via line 20to the etherification zone 14 for processing therein has a totalnitrogen content less than 2 ppm wherein the nitriles content is lessthan 1 ppm, a mercaptan content of less than 1 ppm, and a water contentof less than 1 ppm. The purified feedstock from absorption zone 30 isdelivered to the etherification zone 14 via line 20 wherein thefeedstock is processed under typical etherification conditions in thepresence of a catalyst so as to produce ether-rich additives,particularly, MTBE and TAME. The catalyst employed in the etherificationzone 14 is in the form an acidic ion exchange resin and a suitable ionexchange resin catalyst is commercially available under the nameAMBERLIST from Rohm and Haas or Bayer product K2631. The processconditions in the etherification zone 14 are typically as follows:pressure in the range of 150-300 psi, a temperature in the range of 120°-150° F., a methanol to isoalkene ratio in the range of about 1.05-1.50mole/mole, and a ratio of H₂ to diolefins in the range of about 1.5 to3.2 moles/moles. The ether-rich additive produced in the etherificationzone 14 is discharged via line 36. Depending on the nature of thefeedstock to the etherification zone 14, either MTBE or TAME or amixture of the two is produced and discharged via line 36. For example,if the feed to the etherification zone 14 is substantially rich in C₄,the product produced is MTBE. If the feedstock is an FCC cut rich in C₅,the resulting ether-rich additive is TAME. If the FCC cut feedstock is amixture of C₃ -C₇ hydrocarbons, the product of the etherification zone36 is a mixture of MTBE and TAME compounds.

In accordance with the present invention, it is preferred that thepurification zone 16 be provided with a plurality of absorption zones ortraps 30 for purifying the feedstock delivered via line 18 from the FCCrefining facility 12. By providing a plurality of absorption zones 30the process can be carried out in a continuous manner wherein thefeedstock delivered via line 18 may be treated in one of the absorptionzones 30 while the deactivated purifying alumina medium in the otherabsorption zone 30 is regenerated in accordance with the presentinvention to a superactivated alumina medium as described hereinbelow.

For purposes of illustration the purification zone 16 is illustrated inFIG. 1 as having two absorption zones 30. Each of the absorption zones30 are selectively fed with feedstock from line 18 via lines 38 and 40,respectively. Lines 38 and 40 are provided with valves 42 and 44respectively for selectively feeding the feedstock from line 18 to oneor the other of the absorption zones 30 in a manner to be describedhereinbelow. The discharge from the absorption zones 30, that is, thepurified feedstock, is drawn off via lines 46 and 48 and delivered tofeedline 20 for delivery to the etherification zone 14. Valves 50 and 52are located in lines 46 and 48 respectively and are selectively operablein the manner described hereinbelow.

Sensor 34 is connected to line 20 and monitors the purity of thedischarge from the absorption zones 30 in order to assure that thecontent of nitrogen, nitriles, mercaptan and water in the purifiedfeedstock delivered to the etherification zone 14 meet the purificationlevels described above. The sensor 34, which is commercially availableand the details of which form no part of the present invention, comparesthe measured values of the nitrogen compounds, nitriles, mercaptan andwater in the feedstock in line 20 to a fixed value concentration havingthe values described above with regard to the feedstock to theetherification zone. By monitoring the discharge from the absorptiontraps 30 in the manner aforesaid, it can be determined when one of theparticulate mediums in one of the absorption traps 30 is spent. Uponsensing that the medium 32 in one of the zones 30 is spent, the sensor,through suitable control means available commercially, may activatevalves 42, 44, 50, 52 so as to divert the flow of feed from line 18 tothe other of the zones 30 wherein the process can continue in anuninterrupted manner. The spent particulate medium in the zone or trap30 not in use in the etherification process can then be regenerated inaccordance with the present invention in the manner describedhereinbelow.

In accordance with the present invention, the spent particulate media isregenerated by first draining any hydrocarbon feed in the absorptionzone 30 from the absorption zone via conduits 54 and 56 to sump 58.Lines 54 and 56 are provided with valves 60 and 62 which are selectivelyoperated by the sensor means 34 in a known manner. Once the hydrocarbonmedium is drained from the particles within the absorption zone 30, theparticles are flushed and dried with an inert gas delivered from asource 64 via line 66 which is provided with valve 68. The inert gas ispreferably at a temperature of less than 122° F., more preferably lessthan 110° F.

The dried particles are then treated in a washing process whichsuperactivates and regenerates the particulate medium for further use inthe process. Such treatment removes carbonaceous materials, typicallypolymer precursors, which inhibit the operation of the porous particlesin purifying the liquid hydrocarbon feedstock. This treatment alsoserves to increase the surface area of the porous particles therebyfurther improving the activity of the porous particles. Such treatmentis preferably carried out at temperatures that avoid the formation anddeposition of polymer materials within the particles.

According to the invention, the porous particles are treated with asuperactivating material which may preferably be selected from the groupconsisting of organic solvent, air, mixtures of water vapor and air, andcombinations of the foregoing. The temperatures employed during thewashing step differ depending upon which superactivating material(s) isused. A discussion of the use of an organic solvent, which maypreferably be toluene, follows.

After the porous particles are dried, the particulate medium issubjected to a two-step washing process for regenerating the medium to asuperactivated medium for further use in the process. In accordance withthe present invention, the dried medium is washed with an organicsolvent, preferably toluene, under controlled temperature conditions soas to flush polymer precursors from the medium. It is critical that thetemperature in this stage of regeneration be maintained at a temperatureless than the temperature which would lead to polymerization of thepolymer precursors captive within the medium. Generally, a temperatureof less than 122° F. is sufficient; however, a lower temperature may berequired depending on the nature of the feedstock treated in theabsorption zones 30. With reference to FIG. 1, and for purposes ofillustration, the toluene solvent may be delivered from a source 70 viaa line 72 provided with valve 74 to the alumina medium for washing same.The used solvent discharged via conduit 54 is monitored by sensor 76 soas to determine when this first step washing operation is completed. Forexample, it has been found that when flushing the medium with thetoluene solvent, the discharged solvent is initially brownish in coloras the polymer precursors are removed and the solvent lightens in coloras the amount of polymer precursors removed decreases. Therefore, bymonitoring the color of the discharged solvent the first step flushingoperation can be completed when the discharged solvent runssubstantially clear. This color change can be monitored by sensor 76which can be any suitable commercially available device. Once thepolymer precursors have been substantially removed the medium isthereafter washed again with the organic solvent at an elevatedtemperature of between about 140°-250° F. so as to dissolve any polymersformed in the alumina medium during feedstock purification and the firststage washing. This second stage washing is continued until thedischarged solvent again runs substantially clean in the mannerdescribed above with regard to the first stage washing and sensorelement 76. In accordance with the present invention, the solvent ispassed through the particulate medium at a ratio with respect to thevolume of porous particles in the zone 30 of greater than 4 volumes ofsolvent per volume of particles. The washed, superactivated particulatemedium is thereafter dried with inert gas supplied via line 66 fromsource 64 at a temperature of typically between 220° and 500° F. andpreferably in two steps from a lower temperature to a highertemperature. After drying, the superactivated alumina medium is cooledand is now ready for use and/or reuse in the etherification process ofthe present invention.

Alternatively, as set forth above, the particulate medium can beregenerated using mixtures of water vapor and air. It has been found,according to the invention, that superactivation and/or regeneration ofthe particulate medium with water vapor-air mixtures at the indicatedtemperatures provides excellent increase in surface area of theparticulate medium, thereby greatly increasing and/or restoring theability of the medium to purify hydrocarbon feedstocks before they aretreated with etherification catalysts. As above, the spent particulatemedium is preferably dried with an inert gas such as, for example,nitrogen, at temperatures preferably less than 122° F. and morepreferably less than 110° F. The dried porous particles are thenpreferably washed with a mixture of water vapor and air at a temperaturepreferably greater than about 482° F. (250° C.) and more preferably at atemperature of about between 482° F. and 662° F. so as to removecarbonaceous materials including polymer precursors and to increase thesurface area of the particulate medium. Also, it has been found thatsuch treatment, advantageously, does not substantially alter themorphology of the particulate material. In accordance with thisembodiment, the surface area of a spent particulate can be 95% restoredover a washing time of about between 10 to 24 hours.

Alternatively, air can be used as the superactivating material if thewashing step is carried out at a relatively high temperature of about752° F.

Finally, it has been found that excellent results may also be obtainedby combining the use of an organic solvent and mixtures of water vaporand air. In accordance with this embodiment, spent particulate medium isinitially dried as above with inert gas. The porous particles are thentreated with the organic solvent at a temperature of less than about122° F. so as to remove polymer precursors from the particles. Thesewashed particles are thereafter again washed, with water vapor and air,at a temperature of about between 482° F. to 662° F. Water vapor and airare preferably provided in a mixture having a molar ratio of air towater vapor of about between 0.1 to 10. This combination of washing withsolvent and with water vapor and air mixtures provides excellent resultsin that polymer precursors are removed and the surface area of theparticulate material is regenerated. Of course, using twosuperactivating materials adds to the cost of the process.

Water vapor and air mixtures may suitably be fed to trap zone 30 insubstantially the same manner as organic solvent, as discussed above.

It should be noted that the superactivated particulate medium of thepresent invention may suitably be provided from commercial porousparticles including particulate alumina, silica, zeolite, and mixturesthereof, by treating such commercial porous particles withsuperactivating materials at the preferred temperatures as set forthabove so as to remove undesirable materials from the particles and toincrease the surface area thereof.

The sensor 34 operates valves 42, 44, 50, 52, 60, 62, 68, and 74 throughsuitable control means known in the art (shown by dash lines) forselectively controlling the flow of the feedstock via line 18, inert gasvia lines 66 and solvent via lines 72 during the various operationstages of the process of the present invention.

For clarity, the process of the present invention will now be describedin a step by step manner with reference to an embodiment wherein theporous particles are alumina and the superactivating material istoluene. With valves 42 and 50 in their open position and valves and 44and 52 in their closed position, feedstock from FCC refining facility 12is delivered via line 18 into one of the absorption traps 30 ofpurification zone 16 for contacting the feed with the alumina medium 32in the trap 30. The purified discharge from the trap 30 is delivered vialine 20 to the etherification zone 14 for processing the same for theproduction of ether-rich additives. In accordance with the presentinvention, the feedstock fed to the etherification zone 14 via line 20has the maximum nitrogen content, nitrile content, mercaptan content andwater content set forth above. Sensor 34 continually monitors thepurified feedstock in line 20 in order to insure the necessary purity.When the measured values of nitrogen, nitriles, mercaptan and waterapproaches a fixed value the sensor, sensing the foregoing withassociated control means closes valves 42 and 50 and opens valves 44 and52 so as to divert flow of the feedstock in line 18 to another of theabsorption traps 30 within purification zone 16. Thus, the feed to theetherification zone 14 is continuous and non-interrupted. The spentalumina medium in the first absorption trap 30 is thereafter regeneratedby the sequential steps of drying with inert gas and two-step washingwith organic solvent in the manner described in detail above. When thealumina medium in the second absorption trap becomes spent as determinedby sensor 34, valves 44 and 52 are closed and valves 42 and 50 areopened so as to direct the feedstock from line 18 through the nowregenerated alumina medium in the first absorption zone 30. The spentalumina in the second zone may now be regenerated in the mannerdescribed above. It should be appreciated that the number of absorptionzones 30 may be increased as required so as to insure continuousoperation of the process and allow for sufficient regeneration of thespent alumina prior to the need for using the spent alumina again in theprocess scheme.

Of course, the process follows substantially the same steps as set forthabove when other porous particles are to be employed, and also whenother superactivating materials are to be employed.

As can be seen from the foregoing, the process of the present inventionallows for the pretreatment of the feedstock to the etherification zonein a continuous uninterrupted manner. The advantages and superiorresults obtained by the process of the present invention will be madeclear hereinbelow from a consideration of the following illustrativeexamples.

EXAMPLE I

In order to demonstrate the poisoning effect of nitrogen compounds andparticularly nitriles such as propionitriles and acetonitriles on thecatalyst employed in the etherification process, an untreated FCCfeedstock rich in C₅ and having the composition set forth in Table Ibelow was subjected to etherification in the presence of an AMBERLIST orBayer product K2631 ion exchange catalyst under the process andconditions set forth below in Table II. FIG. 2 shows the conversion ofthe feedstock to the ether-enriched product TAME over time. In order todemonstrate the benefits of pretreatment in accordance with the presentinvention, the same feedstock was pretreated with a porous alumina bed(SELEXSORB CD alumina sold by ALCOA) to obtain a purified feedstockhaving the concentration of mercaptan, total nitrogen, and nitrileconcentration described below in Table I. This purified feedstock wasthereafter subjected to etherification under the same process conditionsset forth in Table II. The results of the effect of this feedstock onthe feedstock conversion to TAME and thus the deterioration of thecatalyst used in the etherification process is illustrated in FIG. 2. Itcan be seen from FIG. 2 that after 60 days the effectiveness onconversion of the catalyst employed in the etherification process whenprocessing a purified feedstock treated in accordance with the presentinvention is substantially identical to that obtained from the virgincatalyst while the conversion effectiveness of the catalyst whenprocessing a feedstock which was not treated in accordance with thepresent invention decreases substantially over time. This exampleclearly illustrates the effectiveness of the pretreatment of thefeedstock in accordance with the present invention to remove nitrogen,nitrile, mercaptan and water in accordance with the present invention.

                  TABLE I                                                         ______________________________________                                        FEEDING         UNTREATED   TREATED                                           ______________________________________                                        Isobutene (% wt)                                                                              8.20        8.00                                              Isoamylenes (% wt)                                                                            10.10       10.10                                             Diolefins (% wt)                                                                              0.83        0.77                                              Mercaptan (ppm) 5.00        less than 1                                       Nitrogen Total (ppm)                                                                          18.00       less than 2                                       Nitriles (ppm)  17.00       less than 1                                       Nitrogen Basic (ppm)                                                                          less than 1 less than 1                                       ______________________________________                                    

                  TABLE II                                                        ______________________________________                                        Temperature of feeding 132 degrees F                                          Process Pressure       175-200 psig                                           LHSV                   2 V/V/hr                                               Ratio of MeOH/ISOALKENES                                                                             1.05 ml/ml                                             ______________________________________                                    

EXAMPLE II

In order to demonstrate the efficiency of the regeneration process ofthe present invention for regenerating a porous alumina medium used inthe process of the present invention, a spent alumina medium used in theprocess of the present invention was regenerated with organic solvent(toluene) in accordance with the present invention and compared to a newvirgin alumina product. The alumina medium employed was a commerciallyavailable alumina medium sold by ALCOA under the name SELEXSORB CD. Thespent alumina medium was processed in accordance with the parameters setforth below in Table III. The spent alumina medium was first drained ofall liquid hydrocarbon feedstock and thereafter dried with an inert gas,nitrogen, at a temperature of 100° F. for 1 hour. The dried aluminamedium was thereafter washed with toluene in the first stage at atemperature of 100° F. for 2.5 hours. The volume of toluene employed inthe first step washing operation was in a ratio of 5 volumes of tolueneper volume of catalyst. The alumina medium was thereafter subjected to asecond washing step at a temperature of 175° F. for an additional periodof 2.5 hours. The volume of solvent employed in the second washing stepwas identical to that employed in the first washing step. The aluminamedium was thereafter purged and dried for 4 hours with nitrogen at atemperature of 250° F. and thereafter the temperature of the inert gaswas raised to 500° F. and the alumina was dried for 12 hours resultingin a superactivated alumina product in accordance with the presentinvention.

                  TABLE III                                                       ______________________________________                                                                         TOLUENE                                      TIME (H)      TEMP (F)  N2(N/H)  (L/H)                                        ______________________________________                                        Drying  1         100       180-300                                                                              --                                         Washing 1                                                                             2.5       100       --     5                                          Washing 2                                                                             2.5       175       --     5                                          Purging 4         248       180-300                                                                              --                                         Desorption                                                                            12        500       180-300                                           ______________________________________                                    

The regenerated alumina medium was thereafter used to treat thefeedstock described above in Example I and compared to a virgin aluminamedium used to pretreat the same feedstock under the conditionsdescribed above in Example I. FIG. 3 shows the results of this test. Itis clear from FIG. 3 that the alumina medium regenerated in accordancewith the process of the present invention (curve A) exhibits superiorabsorption capabilities for nitrogen and nitriles when compared toconventional virgin alumina (curve B).

EXAMPLE III

Tests were run using commercially available alumina (SELEXSORB CD fromALCOA) having a surface area of 305 m² /g and a carbon content of lessthan 1% wt in a pilot absorbing plant having a capacity of 1 liter. Theplant operation conditions were flow between 3.4 to 5 lt/h, LHSV of 5.4v/v/h (1 cycle to 3.4 v/v/h), pressure of 250 psig, temperature of 100degrees F. and cycle time of 30-36 hours. After six cycles of operationthe alumina was substantially spent.

Another sample of the alumina was placed in a furnace and a watervapor-air mixture was injected to the furnace at different temperaturesvalues. The conditions for the formation of the water vapor-air mixturewere as follows:

Ratio liquid water to air: 1:1 (by volume)

absolute pressure of the system: 693 mmHg

Flow of liquid water used: 5 cc/min.

Flow of air used: 5 cc/min.

time of operation: 18 hrs.

Table IV shows the results of washing the spent alumina with the watervapor-air mixture at different temperatures, and FIGS. 4 and 5 show theX ray spectrum diffraction of the alumina which indicates that therewere no significant changes in the morphological structure of thealumina.

                  TABLE IV                                                        ______________________________________                                        TEMPER-   % (Wt) MATERIAL                                                                              SURFACE AREA                                         ATURE (°C.)                                                                      OF CARBON.     m2/gr                                                ______________________________________                                         25       12.2           221                                                  200       11.0           215                                                  260       5.9            240                                                  300       3.4            290                                                  350       2.4            295                                                  400       2.0            295                                                  ______________________________________                                    

Furthermore, superactivated alumina regenerated according to the presentinvention exhibits greatly improved surface area and reduced content ofcarbonaceous materials, and is therefore quite useful in purifyingliquid hydrocarbon feedstocks as described herein.

As can be seen from the foregoing, the process of the present inventionprovides for an effective and economical process for producingether-rich additives such as TAME and MTBE from light hydrocarbonfeedstocks.

This invention may be embodied in other forms or carried out in otherways without departing for the spirit or essential characteristicsthereof. The present embodiment is therefore to be considered as in allrespects illustrative and not restrictive, the scope of the inventionbeing indicated by the appended claims, and all changes which comewithin the meaning and range of equivalency re intended to be embracedtherein.

What is claimed is:
 1. A process for the production of an ether-richadditive, comprising:(a) providing a liquid hydrocarbon feedstockcontaining nitrogen compounds, mercaptan and water; (b) providing aparticulate medium of porous particles selected from the groupconsisting of particles of alumina, silica, zeolite and mixturesthereof; (c) passing said liquid hydrocarbon feedstock through saidparticulate medium so as to remove nitrogen compounds, mercaptan andwater so as to form a purified feedstock substantially free of nitrogencompounds, mercaptan and water wherein the particulate medium becomespoisoned with the nitrogen compounds; (d) treating said purifiedfeedstock with a catalyst under etherification process conditions in thepresence of an isoalkene in an alcohol so as to produce an ether richadditive; (e) regenerating said particulate medium from said poisonedporous particles to form a superactivated particulate medium by thefollowing steps:(1) drying said porous particles by passing an inert gasthrough said porous particles at a temperature of not greater than about122° F.; (2) washing said porous particles with an organic solvent at atemperature of less than about 122° F. so as to flush polymer precursorsfrom said porous particles while substantially avoiding formation ofpolymers within said porous particles; (3) sensing when said porousparticles are substantially free of said polymer precursors; and (4)thereafter further flushing said porous particles with said organicsolvent at a temperature of about between 140° F. to 250° F. so as todissolve polymers within said porous particles while maintaining saidsolvent in a liquid phase.
 2. A process according to claim 1, whereinsaid sensing comprises the steps of:(a) measuring the concentration ofnitrogen compounds, mercaptan and water in said purified feedstockdownstream of said one superactivated particulate medium; and (b)comparing the measured value to a fixed value concentration of nitrogencompounds, mercaptan and water.
 3. A process according to claim 1,wherein said inert gas is nitrogen.
 4. A process for the production ofan ether-rich additive, comprising:(a) providing a liquid hydrocarbonfeedstock containing nitrogen compounds, mercaptan and water; (b)providing a particulate medium of porous particles selected from thegroup consisting of particles of alumina, silica, zeolite and mixturesthereof; (c) passing said liquid hydrocarbon feedstock through saidparticulate medium so as to remove nitrogen compounds, mercaptan andwater so as to form a purified feedstock substantially free of nitrogencompounds, mercaptan and water wherein the particulate medium becomespoisoned with the nitrogen compounds; (d) treating said purifiedfeedstock with a catalyst under etherification process conditions in thepresence of an isoalkene in an alcohol so as to produce an ether-richadditive; (e) regenerating said particulate medium from said poisonedporous particles to form a superactivated particulate medium by thefollowing steps:(1) drying said porous particles by passing an inert gasthrough said porous particles at a temperature of not greater than about122° F.; and (2) washing said porous particles with a mixture of watervapor and air at a temperature of at least about 482° F. so as to removecarbonaceous materials from said porous particles and to increasesurface area of said porous particles without substantially modifyingmorphology structure of said porous particles until said porousparticles are substantially free of said carbonaceous materials.
 5. Aprocess according to claim 4, wherein said washing is carried out at atemperature of about between 482° F. to 662° F.
 6. A process accordingto claim 4, wherein said mixture of water vapor to air is supplied at amolar ratio of air to water vapor of about between 0.1 to
 10. 7. Aprocess for the production of an ether-rich additive, comprising:(a)providing a liquid hydrocarbon feedstock containing nitrogen compounds,mercaptan and water; (b) providing a particulate medium of porousparticles selected from the group consisting of particles of alumina,silica, zeolite and mixtures thereof; (c) passing said liquidhydrocarbon feedstock through said particulate medium so as to removenitrogen compounds, mercaptan and water so as to form a purifiedfeedstock substantially free of nitrogen compounds, mercaptan and waterwherein the particulate medium becomes poisoned with the nitrogencompounds; (d) treating said purified feedstock with a catalyst underetherification process conditions in the presence of an isoalkene in analcohol so as to produce an ether-rich additive; (e) regenerating saidparticulate medium from said poisoned porous particles to form asuperactivated particulate medium by the following steps: (1) dryingsaid porous particles by passing an inert gas through said porousparticles at a temperature of not greater than about 122° F.; and (2)washing said porous particles with air at a temperature of at leastabout 752° F. so as to remove carbonaceous materials from said porousparticles and to increase surface area of said porous particles withoutsubstantially modifying morphology structure of said porous particlesuntil said porous particles are substantially free of said carbonaceousmaterials.
 8. A process for the production of an ether-rich additive,comprising:(a) providing a liquid hydrocarbon feedstock containingnitrogen compounds, mercaptan and water; (b) providing a particulatemedium of porous particles selected from the group consisting ofparticles of alumina, silica, zeolite and mixtures thereof; (c) passingsaid liquid hydrocarbon feedstock through said particulate medium so asto remove nitrogen compounds, mercaptan and water so as to form apurified feedstock substantially free of nitrogen compounds, mercaptanand water wherein the particulate medium becomes poisoned with thenitrogen compounds; (d) treating said purified feedstock with a catalystunder etherification process conditions in the presence of an isoalkenein an alcohol so as to produce an ether-rich additive; (e) regeneratingsaid particulate medium from said poisoned porous particles to form asuperactivated particulate medium by the following steps:(1) drying saidporous particles by passing an inert gas through said porous particlesat a temperature of not greater than about 122° F.; (2) washing saidporous particles with an organic solvent at a temperature of less thanabout 122° F. so as to flush polymer precursors from said porousparticles while substantially avoiding formation of polymers within saidporous particles; (3) sensing when said porous particles aresubstantially free of said polymer precursors; and (4) thereafterfurther flushing said porous particles with a mixture of water vapor andair at a temperature of at least about 482° F. to further removecarbonaceous materials including polymer precursors from said porousparticles and to increase surface area of said porous particles withoutsubstantially modifying morphology structure of said porous.
 9. Aprocess according to claim 8 wherein said organic solvent is toluene.10. A process according to claim 8, wherein said further flushing stepis carried out at a temperature of about between 482° F. and 662° F. 11.A process according to claim 8, wherein the step of passing said liquidhydrocarbon feedstock through said superactivated particulate medium iscarried out under the following conditions:pressure in the range ofabout between 100-300 psi, temperature in the range of about between50°-200° F. in a liquid space velocity (LHSV) in the range of aboutbetween 1.0-5.5 V/V/hr.
 12. A process according to claim 8, wherein theetherification process conditions comprise treating said purifiedfeedstock at a pressure in the range of about between 150-300 psi, atemperature in the range of about between 120°-150° F,. a methanol toisoalkene ratio in the range of about between 1.05-1.50 mole/mole, and aratio of H₂ to diolefins in the range of about 1.5 to about 3.2mole/mole.
 13. A process according to claim 8, further including thesteps of:(a) providing a plurality of superactivated particulatemediums; (b) passing said liquid hydrocarbon feedstock through one ofsaid plurality of superactivated particulate mediums; (c) sensing whensaid one of said plurality of superactivated particulate mediums isspent; (d) thereafter passing said liquid hydrocarbon feedstock throughanother of said plurality of superactivated particulate mediums; and (e)regenerating said spent superactivated particulate medium.
 14. A processaccording to claim 8, wherein said nitrogen compounds are in the form ofnitriles.
 15. A process according to claim 8, wherein said liquidhydrocarbon feedstock comprises a hydrocarbon stream of an FCC lightnaphtha cut.
 16. A process according to claim 15, wherein the lightnaphtha cut is a C₃ -C₇ cut.
 17. A process according to claim 16,wherein said light naphtha cut is substantially a C₄ and C₅ cut.
 18. Aprocess according to claim 8, wherein said catalyst is an ion exchangeresin catalyst.
 19. A process according to claim 8, wherein saidether-rich additive is MTBE, TAME or mixtures thereof.
 20. A processaccording to claim 8, wherein said liquid hydrocarbon feedstock is anFCC C₃ -C₇ feedstock having a nitrogen content of grater than 2 ppm. 21.A process according to claim 20, wherein the feedstock has a watercontent of greater than about 2 ppm.
 22. A process according to claim21, wherein said liquid hydrocarbon feedstock has a mercaptan content ofgreater than 1 about ppm.
 23. A process according to claim 8, whereinsaid purified feedstock has nitrogen content of less than about 2 ppm, amercaptan content of less than about 1 ppm and a water content of lessthan about 1 ppm.
 24. A process according to claim 8, wherein saidliquid hydrocarbon feedstock contains from about 10-15 wt. % isobutene,from about 7-14% isoamylenes, from about 0.5-1.0 wt. % diolefins, andfrom about 17 to about 20 ppm nitrogen, and wherein about 15-17 pm ofsaid nitrogen is in the form of nitriles.